4x dk + paladin/priest/shaman
4x ret + dk
4-5x shaman
4x shaman + insert caster or healer (seen boomkin, hpally, resto druid)
Multi class melee team (ex: warrior, enhance shaman, dk x 2/dk + feral/dk+ret, healer)
Boomkins (though they are not the greatest now)
Multiple feral druids

There are too many options really, but for just getting into pvp i'd suggest sticking with your shaman or rolling dk/rets or healer/dks